Photoelectric sound pick-up



Aug. 3, 1937. E. N. JOHNSON PHOTOELECTRIC SOUND PICK-UP Filed Oct. 8, 19

Far 32 Patented Aug. 3, 1937 UNITED STATES 2,088,960 PHOTOELECTBJC SOUNDPICK-UP Edward Noel Joh son, JohannesburgUnionof South AfricaApplication October 8, 1935, Serial No. 44,120 In the Union of SouthAfrica October 6, 1934 12 Claims. (Cl. 179 -1011541) The presentinvention relates to sound pick-ups of the kind in which the oscillatingstylus-carrier carries a mirror whereby a beam of light is oscillatedcorrespondingly with the stylus and in turn actuates a photo-electriccell.

The object of the invention is to provide a stylus carrier for such apick-up which has notably small mass and moment of inertia. and in whichthe centralizing force can be made low enough to permit the stylus tofollow the sound track with extreme accuracy.

According to the invention there is provided a stylus carrier comprisinga spindle mounted on the tone arm to oscillate about its axis and 5comprising also means to secure a stylus in a position perpendicular tosaid axis, a mirror on said spindle, and means whereby the carrier iselastically centralized and its kinetic energy is absorbed.

The means for securing the stylus may comprise a socket arranged betweenthe ends of the spindle, rigid with and perpendicular thereto, and aclamping screw entering one end of the spindle. The centralizing of thestylus carrier and its damping may be effected by separate means, butconveniently there is provided a hole in the tone arm through which thestylus socket extends and there is compressed within the hole and aroundthe socket a sleeve of material such as rubber which acts as a spring tocentralize the carrier and also as a damper for absorbing its kineticenergy.

' The means for mounting the spindle may comprise rubber sleeving on thespindle, opposite rigid half bearing members forced on to the sleevingto compress it, and means to fix said members in the compressingposition. said bearing members may be pivoted to the tone arm and swungabout their pivots to bring them into compressing contact with thesleeving. The half bearing members are surmounted by a cap plate, andbolts serve to position the halfbearings in their sleeve-compressingposition and to clamp said cap plate and said members to the tone arm.

The invention further comprises the separate stylus carrier as hereafterdescribed.

An example of the invention is shown in the accompanying drawing, inwhich:

Figure I is a dismembered view of the end of the tone arm and the partsassociated there with.

Figure 11 is a end view of Figure I with the parts assembled.

Figure III is a vertical cross section on 111-,-

55 III, Figure I.

.IV illu trates th p rat n f t e de- I Vice. L

2 indicates the end tithe tone m? 3. 3 hal bearin members for thestylus. c rier; a d 4 a cap plate. by whichsaid members are s r d to thetone arm.

The stylus carrier comprises the spind e 5; the endsof which are adaptedto act as the ournals of a rubber bearing and ar fitte with the rubberbearing sleeves 6, .6. :The members .3, 3 areformed with half roundgrooves I which engage and compress the sleeves 6, 6. To iacili tatesuch compression and the accurate positioning of the stylus carrier, themembers 3, .3 are pivoted on pins Bprojecting up from the tone arm. Themembers 3 are first swung apart on said pivots sufliciently to admit thespindle 5 and-its sleeves 6. They are then pressed towardsone anothersuiiiciently to compress and grip thesleeves and are there held by thefitting bolts Ewhich pass through the tone arm, said members and the cap.4. The parts are finally secured by the nuts Ill. The rubber sleeves 6'permit the spindle to oscillate to the neces-. sary extent about itsaxis ll, without material lateral displacement from said axis. .One endI2 of the spindle is bored and screw threaded to receive the stylusclamping screw l3. At the.

other .end,and near to the axis ll, there is rigidly fixed the mirror l4by which alight beam is deflected.

The stylus carrier further includes the stylus socket l 5, which isrigid with the spindle and projects at right angles to the latter. Saidsocket is formed witha bore [6 to receive the stylus llysaid bore I6intersecting and extending upward beyond the bore for the clampingscrew- 13* so that the stylus bears against the wall of.

its socket bot-h abovea-nd below the clamping screw. l r

The socket I5 passes through a hole l8-in the tone arm. Compressed insaid hole and around the socket is a sleeve IQ of rubberor othermaterial capable of functioning asa spring tocexitralize the stylusandas a damping medium to dissipate the kinetic energy which the styluscarrier and the stylus continually acquire when the pick-up is-in'o'peration'.

In use, the parts are assembled as indicated in Figures. II and III sothat the stylus carrier can oscillate about its axis It, subject to thecentralizing and damping effect of the sleeve l9; It is thus scillatedby the y us follow n t e laterally out sound track of agramophonerecord. A'stationary beam or lightTZ I. Fi u V; is irectedonto the mirror l4 and by it is oscillated correspondingly withoscillations of the stylus. The oscillating beam after modulation, as bya fixed cut-01f 2|, is caused so to influence photoelectric apparatus 22as to produce electric oscillations which in turn are converted intosound.

It will be noted that a large proportion of the mass of the styluscarrier is concentrated about the axis H and therefore has a lowmomentof inertia. The only members of which the moment of inertia issignificant are the stylus I'I itself and the stylus socket IS. Themoment of inertia of the latter is however very small and thecentralizing and damping force can consequently be made small so thatthe stylus readily follows the full lateral range of the sound trackwithout materially tending to oscillate the tone arm itself.

I claim:

1. In a photo-electric sound pick-upthe combination with a support, of astylus carrier comprising a straights'pindle mounted in the support tooscillate about its longitudinal axis and comprising also a) transversestylus socket, the spindle having an 'axial .bore intersecting thestylus socket and screw threaded to receive a stylus clamping screw, amirror rigid with the spindle and having its reflecting surfaceapproximately in a plane including the spindle axis, and means wherebythe carrier iselastically centralized and its kinetic energy isabsorbed.

2. In a photo-electric sound pick-up, thecom-v bination with a supportof a stylus carrier comprising a spindle mounted on the support tooscillate about its axis and comprising also a stylus socket rigidlyextending transversely from the spindle which is bored at one end toreceive a clamping screw for securing the stylus in said socket;.amirror rigid with thespindle and having its reflecting surfaceapproximately in a plane including the spindle axis, and means wherebythe carrier is elastically centralized and its kinetic energy isabsorbed.

3. In a photo-electric sound pick-up, the com l 4. In a photo-electricsound pick-up, the combination with a support of a stylus carriercomprising a spindle mounted on the support to 05 cillate about itsaxis, and comprising also a stylus socket rigidly extending transverselyfrom the spindle which is bored at one end to receive a clamping screwfor securing the stylus in said socket, amirror rigid with the spindleand having its reflecting surface approximately in a plane including thespindle axis, rubber sleeving on the spindle, opposite half bearingmembers forced onto the sleeving to compress it, means to fix saidmembers in the compressing positio n, and furthermeans whereby thecarrier is elastically centralized and its kinetic energy is absorbed.

5. In a photo-electric sound pick-up, the combination with a support ofa stylus carrier comprising a spindle mounted on the support tooscillate about its axis and comprising also means to secure astylus'ina position transverse toisaid axis, 'a mirror rigid with the'spiiidleand having .prising a spindlemounted on the support to oscillate aboutits axis and comprising also a stylus socket rigidly extendingtransversely from the spindle which is bored at one end to receive aclamping screw for securing the stylus in said socket, a mirror rigidwith the spindle and having its reflecting surface approximately in aplane including the spindle axis/opposite half bearing members which arepivoted on the support and'are swung about their pivots to compress thesleeving, a cap plate, bolts serving to position the half bearingmembers in sleeve compressing relationship and to clamp said cap plateand said members to the support, and further means whereby the carrieris elastically centralized and its kinetic energy 'is absorbed.

7. In a photo-electric sound pick-up, the combination with a support .ofa: stylus carrier comprisingv a spindle mounted on the support tooscillate about its axis and comprising also a stylus socket rigidlyextending transversely from the spindle whichis bored at one end toreceive a clamping screw for securing, the stylus in said socket, amirror rigid with the spindle andhaving its reflecting surfaceapproximately in a plane including the spindle axis, and means whichbearson the socket at opposite sides in the direction of itsoscillationwhereby the carrier is elastically centralized, and means whereby itskinetic energy is absorbed. c

8. In aphoto-electric sound pick-up, the combination with a support of astylus carrier comprising a spindle mounted on the support to oscillateabout its axis and comprising also a stylus socket rigidly extendingtransversely from the spindle which is bored at one end to receive aclamping screw for securing the stylus in said socket, a mirror rigidwith the spindle and having its reflecting surface approximately in aplane including the spindle axis, rubber sleeving on the spindle,opposite half bearing members forced onto the sleeving to compress it,means to fix said members 'in the compressing position and means whichbears on the socket at opposite sides in the direction of itsoscillation whereby the carrier is elastically centralized, and meanswhereby its kinetic energy is absorbed.

9. In a photo-electric sound pick-up, the combination with a support of'a'stylus carrier comprising a spindle mounted 'on the support tooscillate about its axis and comprising also a stylus socket rigidlyextending transversely from the spindle whiclris bored at one end toreceive aclamping screw for securing the stylus in said socket, a mirrorrigid withthe spindle and having its reflecting surface approximately ina plane including the spindle axis, 'the' support having'a hole throughwhich the stylus socket extends, and a sleeve compressed into theholeand 10. In a photo-electric sound pick-up," the comspindle which isbored at one end to receive a clamping screw for securing the stylus insaid socket, a mirror rigid with the spindle and having its reflectingsurface approximately in a plane including the spindle axis, rubbersleeving on the spindle, opposite half bearing members forced onto thesleeving to compress it, means to fix said members in the compressingposition, the support having a hole through which the stylus socketextends, and a sleeve compressed into the hole and around the socket,said sleeve being of material having elastic and energyabsorbingproperties.

11. A pick-up stylus carrier comprising a spindle, a stylus-receivingsocket integral with the spindle and extending transversely therefrom,the spindle having an axial bore extending from one end to intersect thestylus socket and screw threaded suitably to receive a stylus clampingscrew, and a mirror rigid with the spindle and. having its reflectingsurface approximately in a plane including the spindle axis.

12. The carrier claimed in claim 11 in which the stylus-receiving socketis positioned at about the centre of the length of the spindle and theexternal surface of the spindle from said socket to its ends is: a plaincylindrical journal surface of uniform diameter.

EDWARD NOEL JOHNSON.

